Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC) is performed in patients with peritoneal tumors. Classically, this procedure is prolonged in duration and involves significant fluid shifts. Patients receive a large amount of volume replacement during this procedure (between 10 and 20 liters). The traditional methods to monitor adequacy of volume replacement are measurement of urine output and central venous pressure. There are drawbacks of any method of intravascular volume status measurement which may lead to over or under replacement of fluids. If fluid replacement is underestimated, the patient may suffer from adverse effects such as hypotension and renal dysfunction. However, the excessive administration of fluids may lead to other adverse events, including cardiac dysrhythmias and heart failure. The hypothesis of this study is that patients in whom volume status is maintained by utilizing a transesophageal echocardiogram will have better maintenance of fluid status while avoiding intravascular volume overload.